SUMMARY/ABSTRACT There has been a dramatic rise in the number of severe fungal infections due to a constant increase in the number of individuals who are immunocompromised. Strong similarities in the basic eukaryotic metabolic pathways between fungi and mammalian cells have hindered the development of antifungal agents because many compounds that are effective at inhibiting fungal growth are also toxic to host cells. It is becoming clear that novel antifungal agents alone are unlikely to significantly reduce the mortality rate of fungal infections without the aid of new therapeutic approaches. Promising alternative approaches include combining current antifungal treatments with agents that enhance the host immune system's ability to eliminate the microbe or disrupt an interspecies molecular interaction that governs invasion. These approaches require a detailed understanding of the complex interaction between host and pathogen. This proposal will focus on three emerging fungal pathogens - Scedosporium spp, Candida auris and Mucorales fungi. Infections with these three phylogenetically distinct pathogens frequently fail to respond to currently available antifungal therapy and are therefore associated with extremely high mortality rates. Here we will combine dual-species RNA-seq, comparative genome analysis, established animal models and fungal genetics to systematically and comprehensively analyze the host-pathogen interactions for each class. Analyzing all three different types of fungi using the same approach will enable us to define commonalities as well as key differences among the organisms and the responses they elicit in the host. The proposed studies will provide a wealth of information regarding gene function and regulation in both the fungus and the host and will likely lead to the identification of novel therapeutic targets to treat this increasingly serious cause of human disease.